Sternwarte Universitšt Bonn

BUSCA Manual

Oliver Cordes & Ana Guijarro

Bonn&Calar Alto

Calar Alto Observatory

Table of contents

  • Instruction for technician

  • Startup (for observers)
    1. execute the command start_busca in the instrument window or in a xterm; the BUSCA GUI appears on the screen
    2. the initialization is finished when Program initialized! appears in the status line. (In case error dialog boxes pop up, click OK .)
    3. if the status window CCD status is idle, choose CCD->Voltages on from the menu, the CCD should switch to continuous scan
    4. check the temperatures and the LN2 status of all channels in the status window (should be green or OK)
    5. enter the observer data (only necessary, if you start the software for the first time)
    6. the system is now ready to observe
    7. if you want to activate the sound output of the software you have to switch on the speakers above the monitors and to start the program audiocontrol in a xterm and press the button headphones

    Data aquisition
    1. enter the exposure time and number of exposures you want
    2. choose a filter set
    3. enter the object name or press the button last name on the right side  (the button is orange, if a last name is available)
    4. choose an exposure type
    5. choose the channels you want to read out or press the button all on the right side to select all channels
    6. choose a CCD frame definition
    7. press the button Start Exposure and the exposition begins. During an exposition you can press the buttons BREAK or Pause. BREAK means that you abort the current and following exposure(s). If you press Pause, you can choose: to BREAK, to CONTINUE (e.g. when the dome vignets the pupil and you have to move the slit) the exposition or to begin the READOUT with the exposition time passed.
    8. the exposition is finished, when you see Taking exposure(s) finished! in the status line. If you have pressed BREAK (see above) you will see Taking exposures(s) aborted! You will also hear a double beep and a funny sound if you  have activated the sound output. (see startup procedure )
    9. in any case you can now start a new exposition!


    1. from the menu in Exposure, there is an option to create a focus sequence image manually (BUSCA makes a single exposition and waits until the observer changes the telescope focus manually) and automatically (BUSCA sets the focus for each single exposition).
    2. if there is any connection problem between the telescope and BUSCA, you have to write StopTeleserver in a xterm-window. Then you have to set RESET tecs-dacs-tvg in the workspace of the tvg.
    3. recommended values for a focus sequence image of an open cluster are (WG filters): 5 seconds exposure time, 100 lines to shift, 10 exposures, 24.95 start focus (tube temperature~5 degrees) and a focus increment of 0.05.
    4. the result is an image, which can be analysed with IRAF, imexam, (or MIDAS) to choose the star with the best FWHM.
    5. the telescope does not change the focus automatically due to temperature changes, but you can get an idea of the correct focus from the focus equation (see at the left wall of the observers room in the 2.2m telescope).
    6. IMPORTANT: There is only one focus for all channels, if all filters have the same thickness (e.g. all Stroemgren filters). For other filter sets there exist a different focus, so you have to determine the focus for each filter set!

    Closing (for observers)

    Quit the program , use File->Quit from the menu or press Crtl-Shift-Q

    CCD frame definition

    CCD frame definition means in this case that you have to choose which part of the CCD is to be read out and which readout mode (binning) you want to use. BUSCA has four 4kx4k CCD devices. The pixel scale are 0.17" per pixel. To use the 4kx4k frame or a part of these frame means that you readout the CCD without any binning or with binning 1. For normal use at Calar Alto the CCD is read out in binning 2 mode with a pixel size of 0.34". This also reduce the readout time for the 2kx2k to 2:20s ( ~8min for 4kx4k).

    There two different ways to choose a CCD frame definition:

    1. use a predefined definition
    2. you have to choose one entry from the menubox in the middle of the exposure area labeled CCD-Frame:

    3. make a user specific definition

    Overscan size of full format frame with binning 2 --> [2080:2200,2080:2200]
    Overscan section of the frame with binning 2 --> [2078:2100,1:2100]

    Observer data

    Click to enlarge

    To enter the observer data choose Config->Set observer data from the menu. In the dialogbox  you can enter these parameters:

    Error message

    startup error messages:





    binning binning means that you can combine neighbour pixels together; you get the sum of the fluxes from all pixels; you can also save readout time, but you looses the resolution of the image (binning 2 means, you combine a square of 4 pixels to one pixel)
    CCU CCD Control Unit, all the hardware for controlling the CCDs
    LN2 chemical sign for Liquid Nitrogen, here used for cooling the CCDs
    FOV the Field of View, the area in the sky which is covered by the CCD 
    UC Universal Control, this unit is controlling the filter wheels, the shutter , the temperature of the CCDs and the evaporation rate of the LN2 in the dewars
    continuous scan default mode of the CCDs between 2 exposures, deletes charges of the CCDs